An experimental assessment of observation cross-correlation in dual frequency GPS receivers

摘要

In processing GPS data for precise differentialrnpositioning, modelling considerations underlying thernobservations' variance-covariance matrix generallyrnconcern only the variances of the individual pseudorangernand carrier phase observations, and usually disregard anyrnpossible correlation between different observation types.rnOne of the causes of this correlation is that civilian dualrnfrequency GPS receivers employ particular techniquesrnunder Anti-Spoofing to reconstruct the pseudorange andrncarrier phase observables on the L2 frequency. These socalledrncodeless and semi-codeless techniques may resultrnin correlations between the observation types.rnAccounting for the correlations is crucial in highrnprecision GPS applications to obtain optimal positioningrnestimators.rnAn experiment was carried out recently with seven dualfrequencyrnGPS receivers of different type and makes inrnorder to examine the cross-correlation on pseudorangernand carrier phase observations between the L 1 and L2rnfrequency. With a method for statistical variancerncomponent estimation cross-correlation coefficients wererncomputed. The coefficients between L1 and L2rnpseudorange observations may reach up to 0.75. BetweenrnL1 and L2 carrier phase this figure turns out to be evenrnmore significant for some of the receivers. The resultsrnalso underline that carrier phase cross-correlation is a truernissue as it turns out to be present on all receiversrnconsidered. With these results the currently usedrnstochastic models can be refined and, they may contributernto our knowledge about the receivers' internal processes.